Nitrogen-Doped Graphene Foam As a Metal-Free Electrocatalyst

Abstract

Pt nanoparticles are generally used as the electrocatalyst in proton exchange membrane fuel cells (PEMFCs). However Pt is expensive, and has limited durability due to agglomeration, dissolution, and carbon corrosion in the harsh environment of the fuel cell cathode. Alternative electrocatalysts have been proposed; one of the most popular being Fe/N/C-based electrocatalysts. However, these non-platinum group metal (non-PGM) electrocatalysts struggle to compete with platinum in terms of performance and durability in the acid environment of a PEMFC. In alkaline media, the oxygen reduction reaction (ORR) kinetics are much faster, and this means that non-PGM electrocatalysts can compete with Pt. Until recently, anion exchange membrane fuel cells (AEMFCs) were not considered to be able to compete with PEMFCs. However, recent advances in membrane technology have made them more viable. Here, we show that even a completely metal-free nitrogen-doped carbon can have electrochemical ORR activity comparable to that of platinum. Moreover, we perform electrochemical load-cycle durability tests and show that even after 60,000 potential cycles negligible degradation is observed for this electrocatalyst system in alkaline. In contrast, the performance of Pt is much worse after the same test. In conclusion, non-precious nitrogen-doped graphene foam is a potential electrocatalyst for the oxygen reduction reaction in alkaline anion exchange membrane fuel cells.